In general, a damper includes, for example, a cylinder, a piston slidably inserted into the cylinder, a rod that is inserted into the cylinder and connected to the piston, a rod-side chamber and a piston-side chamber that are divided within the cylinder by the piston, and a damping passage that allows communication between the rod-side chamber and the piston-side chamber. A damping force is exerted in accordance with an extending/contracting operation in which the piston displaces in an axial direction relative to the cylinder to suppress the oscillation of an object to be damped.
The above-described damper exerts a damping force in a direction to suppress extension/contraction during a stroke regardless of whether it extends or contracts. However, for example, in a damper used to damp a building or the like, there are cases in which the oscillation of the building actually cannot be reduced when a damping force is exerted depending on the stroke position. Therefore, for example, in the damper disclosed in JP2007-321909A, a bypass path that bypasses a damping valve at the stroke end is opened to allow communication between the rod-side chamber and the piston-side chamber.